Transformer core clamp connector



Oct. 27, 1959 s. H. WILK ET AL TRANSFORMER coma CLAMP CONNECTOR 2Sheets-Sheet 1 Filed Dec. 29, 1954 a m 5W am a 1 v WH U E IIIIIIIIIIIIIll... n I n z m 2m 4 161W I H F. O 0 Q J 0 ,MM m H 1. E, T W o mgfifillr l 'l l ld-HI PI IH I I IH I0} 4 WM 0 0 0 Q J m M f l lvlhllllllliw easwwaeooo W .71! it Oct. 27, 1959 s. H. WILK ET AL TRANSFORMERCORE CLAMP CONNECTOR 2 Sheets-Sheet 2 Filed Dec. 29, 1954 Edwarc/D.OYYeil,

flaw 9 72,4

United States Patent TRANSFORMER CORE CLAMP CONNECTOR Stanley H. Wilkand Edward D. ONeil, Pittsfield, Mass, assignors to General ElectricCompany, a corporation of New York Application December 29, 1954, SerialNo. 478,318

4 Claims. (Cl. 336-410) This invention relates to stationary electricalinduction apparatus and more in particular to an improved core clampconnector for power transformers.

Power transformer cores are generally comprised of a plurality ofvertical leg sections formed of stacked laminations of magnetic materialwhose ends are joined by horizontal yoke sections also formed of stackedlaminations of magnetic material. In the past these cores have beenclamped together by various means. In one type of clamping means,channel shaped members are placed adjacent to each side of the yokelaminations, and bolts extending through the clamps and yoke hold thecore laminations firmly together. In this type, vertical stresses aresometimes present in the leg laminations due to short circuit forces orlifting forces, since in this case the leg members act as a tie betweenthe clamps. In a second form of clamp, tie rods are provided extendingbetween the top and bottom clamps external to the windings to removethese vertical stresses from the laminations. These outside connectionshave proved to be undesirable, however, especially in high voltage andlarge transformers. In order to eliminate tie rods and stresses in leglaminations, a third type of clamp employs tie plates located inside ofthe windings and adjacent to each side of each core leg. The ends of thetie plates are connected to the bottom and top channel members by meansof bolts extending through the core clamps and into the tie plates.

In the latter type of core clamp, the vertical stresses applied to thecore are absorbed by the bolts holding the tie plates and channelmembers together. In order that each bolt carry its share of anyexisting stresses, the holes through the tie plates must be accuratelypositioned. It has been the practice in the fabrication of such cores,to first assemble the tie plates and drilled channel members on a flatsurface to accurately locate the positions of the holes to be drilled inthe tie plates. The clamp parts are then disassembled and the holesdrilled and tapped in the tie plates. Then a bottom channel member andits associated tie plates are reassembled on a flat surface, and the legand bottom yoke members stacked in place on top of the clamp members.The other bottom channel members and associated tie members are placedon top of the stacked laminations, and the entire assembly is accuratelyaligned to provide the proper distances between the legs and rightangles between the leg members and the bottom yoke. This assembly isthen bolted together and raised to an upright position. Since the finalassembly of the cores generally occurs at another location in the shop,the cores are then transported by means of slings extending around thebottom yokes to a final assembly area. The final assembly consists ofplacing windings over the legs, assembling the top yoke in position, andclamping the top channel members in place. The assembly of thetransformer core having external-tie rods is similar to the abovedescribed method, with the excep- 'tion that no preassembly is required.

2,916,563 Patented Oct. 27, 1959 Although it may be possible to use ajig or template to locate the holes in the tie plates and therebyeliminate the previously mentioned preassembly step, such a jigintroduces additional complications into the assembly. Due to thethinness of the tie plate, a number of smaller bolts are usuallyrequired in order to carry the load, since one large bolt would notengage sutficient threads in the tie plate. The number of bolts variesin different transformers, and the position of the bolts may also varyin different transformers. Similarly the length of the tie plates alsovaries. With such a jig then, the holes would have to be accuratelyaligned with respect to each other, and the holes in the clamp memberswould have to correspond exactly with the holes in the tie plates. Thiswould result in the necessity for a relatively complicated jig for eachtransformer type, and also a necessity for accurately aligning the jigso that the holes in the tie plates correspond to the holes in the clampmembers. From a practical standpoint this method has not been found tobe suitable.

It has been found that the previously described core clamps have severalinherent disadvantages. As previously stated, it is undesirable to havetie rods located outside of the windings. ln the construction of thesetypes of cores a considerable amount of time is required to accuratelyalign the legs and yokes prior to clamping them in position. It has alsobeen difiicult to transport the cores to a final assembly area. Anexcessive amount of space is required for the fabrication of the boltedtie plate type of core due to the initial assembly that must be made,and the preassembly for accurately locating the tie plate holes has beenfound to be time consuming and costly. The first type of clamp also hasthe disadvantage of requiring a bolt hole through the corners of thecore laminations.

These difliculties have been overcome in the present invention byemploying tie plates similar to those previously described, but havingbuttons welded on their ends instead of holes previously drilled andtapped therein. The buttons may be accurately positioned withoutpreassembly by means of a simple jig. The buttons fit into correspondingholes in the channel members. Proper alignment of the core members isthereby assured, and it is merely necessary to establish a right anglebetween one leg and the yoke. As will be described later, the buttonsalso provide for a convenient method of transporting the cores to afinal assembly area.

It is therefore an object of this invention to provide an improved coreclamp connectorfor transformers.

It is also an object to provide an improved core clamp connector fortransformers eliminating the necessity for tie rods external to thewindings between the yoke clamps.

A further object of this invention is to provide a core clamp connectorfor transformers wherein tie plates internal to the windings areconnected to end clamps on the transformer core to remove stresses fromthe core laminations and wherein a minimum amount of time and elfort isrequired to fabricate the cores, and a minimum number of holes arerequired through the core laminations.

A still further objectof this invention is to provide buttons onthe'ends of tie plates in a transformer core clamp connector wherein thebuttons engage holes in the end clamps of the core to prevent liftingand short circuit forces from being induced in the transformer core andto provide an improved method for fabrication of the cores.

This invention will be better understood from the following descriptiontaken in connection with the accompanying drawings and its scope will bepointed out in the appended claims.

In the drawings,

Fig. 1 is a partly broken away side view of a power transformer coreillustrating one embodiment of the core clamp connector of thisinvention;

Fig. 2 is an end view, partly in section, of the transformer core ofFig. 1;

Fig. 3 is a partially exploded view of one end of the transformer coreof Fig. 1;

Fig. 4 is a side View of one form of the core clamp connector of thisinvention, and

Fig. 5 is a perspective view of a top corner of a partially assembledtransformer core illustrating a modification of the core clamp connectorof this invention.

Referring now to the drawings, and more particularly to Figs. 1, 2, and3, a power transformer core is therein illustrated having three legsections 10, 11 and 12 joined by a bottom yoke section 13 and a top yokesection 14. The core sections are formed from stacked laminations of amagnetic material. These core sections may have a cruciform crosssection (as illustrated in Fig. 3), and they may also be provided withducts 16 and 17 extending therethrough. The duct 16 completely separatesthe front half of the core from the back half of the core for thepurpose of circulation of a cooling fluid, and the proper spacingbetween the core halves is provided by means of spacers 18. The duct 17extends through the core at right angles to the duct 16, and providesimproved magnetic characteristics for the core, as well as providing forcoolant fluid circulation and simplifying the construction of the core.The core may also have mitre-joints as illustrated, although any othertype of joint, such as a butt lap joint may be used without departingfrom the scope of this invention. Similarly any other core cross sectionconfiguration may also be employed with the core clamp connector of thisinvention.

For clarity, windings 19, 20, and 21 are shown in phantom in position onlegs 10, 11, and 12 respectively.

In order to hold the core laminations firmly together, tie plates 22 areplaced on each side of the leg laminations, bottom clamp members 23 areplaced on each side of the bottom yoke member 13, and top clamp members24 are placed on each side of the top yoke member 14. The tie plates andtop and bottom clamp members are clamped to the core by means of aplurality of bolts 25 extending through the yokes and legs. In the fullysplit type of core as illustrated, the bolts may pass through the ductsAdditional clamping action may be provided by bolts 26 passing throughthe ends of the clamp members 23 and 24. The top and bottom clampmembers may be any shape giving the necessary strength, such as achannel shape as illustrated in the bottom clamp 23, or an angle shapeas illustrated in the top clamp 24. The'clamp members may also havereinforcing members 27 Welded thereto for additional strength, andplates 28 may be positioned between the ends of the clamp members forthe same purpose.

To facilitate lifting of the transformer, the upper yoke clamps areprovided with a plurality of lifting lugs 29. When a transformer islifted, unless mechanical linkages are provided between the bottom andtop braces, the leg laminations will be subject to the lifting stresses.Similarly, short circuit forces acting on the windings may causestresses in leg laminations'if they are notabsorbed by other means.These stresses are'remoVed-in the present invention by means of buttons30 welded to the ends of the tie plates 22. Holes 31 corresponding tothe buttons 353 are provided in the clamp members 23 and 24. Foradditional mechanical strength of the clamp member holes 31, drilledplates 32 may be welded on the sides of the clamp members. 7

A plurality of spacing blocks 33-are positioned between the sides of theyoke laminations and the top and bottom clamp members in order toprovide space for fl id Gib culation around the core. v

tions, tie plates, and clamp members.

the top clamp members.

When a winding is placed over the core leg, it is of course necessarythat no part of the core leg-have a Width greater than that of thewinding cylinder. This factor limits the maximum length of the topbutton. Referring now to Fig. 4, the top button 40 is shorter than thelower button 30 in order to provide clearance for the Winding cylinder.Due to the decreased length of the top button 40, however, it may bedesirable to weld this button from the back of the tie plate, so thatthe full length of the button may be used as a bearing surface withoutinterference from the weld.

Since the spacing blocks 33 (Figs. 1 and 3) are generally of a standardwidth, and may be of sufiicient width that the hole 31 in the top clampmember 24 does not fully engage the button, it may be necessary to weldthe drilled reinforcing plates 32 on the inner sides of the top clampmembers. v

In the modification of core clamp connector illustrated in Fig. 5, thetop clamp member 24 and reinforcing plate 32 are held firmly against thetie plate 22 by means of a bolt extending into a tapped hole in the topbutton 40. The bolt 50 is provided with a washer 51 or block engagingtheclamp member. The advantages of this modification will be describedlater, and it is to be noted that in Fig. 5 the yoke laminations are notin place.

In the assembly of a transformer core according to this invention, thebuttons are Welded onto the tie plates by means of a spacing jig, andaccurately located corresponding holes are drilled in the clamp members.The jig may be very simple, since it is only necessary to accuratelyestablish the center line. distances between the buttons. The tie platesand clamp members of one side of the transformer are then assembled on aflat surface, and the leg and bottom laminations stacked on the topthereof. Then the tie plates and clamp members for the other side of thecore are placed on top of the stacked laminations. Since the top clampmembers are in place, the proper distance between the leg members isprovided, and it is only necessary to establish a right anglerelationship between the bottom yoke member and one leg.

Having been properly aligned, the core is then clamped together, bymeans of bolts extending through the lamina- If the core is of the splittype, all of these bolts may go through the ducts extending through thecore. Then the entire assembly is placed in an upright position.Although it is not necessary at this time that the top clamp member bebolted in place, it may be desirable, as illustrated in Fig. 5 to holdthe top clamp member in position by means of bolts extending into tappedholes in the top buttons. Since the top clamp members are mounted inposition, transporting the core assembly to a final assembly area may beaccomplished by means of the lifting lugs 29 in The final assemblyconsists of removing the top clamp members, placing windings over thelegs, assembling the top yoke members in place, replacing the top clampmembers, and clamping thetop yoke in place by means of bolts extendingthrough the laminations. Replacement of the top clamp members issimplified by drawing them into place by means ofthe bolts 50. V

The core clamp connector of this invention may be used on solid coretransformers as well as split core transformers, and the core may havemit-re joints, butt lap joints, or any other types of joints. In thec'aseof the fully split transformer cores, no holes are required throughthe laminations for clamping purposes. In the case of solid transformercores, no extra holes are required through the core for holding the tieplates and clamp members together.

While it is preferred that the buttons be welded on the tie plates, thisinvention also contemplates the weldcorresponding holes in the tieplates. In such a case reinforcing plates should be welded to the tieplates.

From the foregoing description, it is seen that this invention providesa transformer core requiring no holes through the laminations forabsorbing short circuit and lifting forces. A minimum of space, effort,and time is required to construct the core, and improved means areprovided for transporting thecore. The alignment of the core issimplified, and no tie rods are required outside of the windings. Thecore is readily adaptable to mass production techniques.

It will be understood, of course, that, while the forms of the inventionherein shown and described constitute preferred embodiments of theinvention, it is not intended herein to illustrate all of the possibleequivalent forms or ramifications of the invention. It will also beunderstood that the words used are words of description rather than oflimitation, and that various changes may be made without departing fromthe spirit and scope of the invention herein disclosed.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A transformer core comprising a plurality of leg sections formed ofstacked laminations of a magnetic material, a plurality of yoke sectionsalso formed of stacked laminations of a magnetic material and joiningthe ends of said leg sections, elongated end clamp members extendingparallel to said yoke members clamping said yoke sections, elongated tieplate members extending parallel to said leg members clamping said legsections, joints between said clamp members and tie plate members aplurality of cylindrical buttons, one of said buttons being rigidlyafiixed to one of said members at each joint of said clamp members andtie plate members and extending perpendicular to said core, said buttonsextending through corresponding holes in the other of said members ateach of said joints.

2. A transformer core comprising a plurality of leg sections formed ofstacked laminations of a magnetic material, a plurality of yoke sectionsalso formed of stacked laminations of a magnetic material and joiningthe ends of said leg sections, an elongated clamp member extending inparallel relationship on each side of each yoke section and clampedthereto by means of bolts extending through said yoke sections, anelongated tie plate member extending in parallel relationship on eachside of each leg section and clamped thereto by means of bolts extendingthrough said leg sections, joints between said clamp members and tieplate members, a plurality of cylindrical buttons, one of said buttonsbeing rigidly aflixed to one of said members at each joint of said clampmembers and said tie plate members and extending perpendicular to saidcore, said buttons extending through corresponding holes in the other ofsaid members at each of said joints.

3. A transformer core comprising a plurality of leg members formed ofstacked laminations of a magnetic material, a plurality of yoke membersformed of stacked laminations of a magnetic material and joining theends of said leg members, elongated tie plates mounted adjacent thesides of said leg members in parallel relation thereto and being clampedthereto by means of bolts extending through said leg members, acylindrical button rigidly afiixed to each end of each of said tieplates and extending outwardly from said leg members, clamping membersextending parallel to said yoke members and being clamped rigidly inrespect thereto by means of bolts passing through said yoke members, andholes in said clamping members into which said buttons extend.

4. A transformer core comprising a plurality of leg members formed ofstacked laminations of a magnetic material, a plurality of yoke membersformed of stacked laminations of a magnetic material and joining theends of said leg members, elongated tie plates mounted adjacent thesides of said leg members in parallel relation thereto and being clampedthereto by means of bolts extending through said leg members, a firstcylindrical button afiixed to the top end of each of said tie plates andextending outwardly from said leg members, a second cylindrical buttonaffixed to the bottom end of each of said tie plates and extendingoutwardly from said leg members, said first buttons having lengthspermitting a winding to be placed over them and onto the respective legmembers, clamping members extending parallel to said yoke members andbeing clamped rigidly in respect thereto by means of bolts passingthrough said yoke members, and holes in said clamping members into whichsaid first and second buttons extend.

References Cited in the file of this patent UNITED STATES PATENTS2,083,354 Whittier June 8, 1937 2,328,228 Pearson Aug. 31, 19432,655,622 Besag et al. Oct. 13, 1953 2,702,375 Johnson Feb. 15, 1955FOREIGN PATENTS 668,990 Great Britain Mar. 26, 1952 862,032 Germany Jan.8, 1953

